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Showing posts from September, 2018

Producing fructophilic Starmerella bacillaris as an active dried wine yeast

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By Karien O'Kennedy
Starmerella bacillaris, previously known as Candida Zemplinina, has received wide spread attention by wine yeast researchers as a result of its fructophilic nature and lower ethanol producing abilities. The yeast occurs naturally in spontaneous fermentations, but to date no commercially produced ADWY starter cultures are available. The aim of this study was to determine if Starm. bacillaris can be desiccated (dried) and rehydrated similarly to Saccharomyces cerevisiae and still have the desired effects in fermentations.For the purpose of this summary only some results of interest will be presented. Refer to the article for full experimental layout and all results. Experimental layout Cell suspensions of five strains of Starm. bacillaris were desiccated in the presence of different trehalose concentrations (10, 20, 30, 40, 50%), by exposure to dry air for 20 hours at 28°C.Cell rehydration was performed at 30, 40 and 50°C for 10, 20 and 30 minutes.Viability was de…

Nitrogen source preference of Starmerella bacillaris during fermentation

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By Karien O'Kennedy
The aim of the study was to investigate the uptake of nitrogen sources by Starm. bacillaris and how it compares to Saccharomyces cerevisiae. The effect on the central carbon metabolite production was also investigated. Experimental layout One S. cerevisiae strain, Uvaferm BC, and two Starm. bacillaris strains were evaluated in this study.Fermentations were conducted in synthetic grape must: SM200.The medium contained equal amounts of glucose and fructose but differentiating amounts of amino acids and ammonium, generating three different musts.Fermentations were conducted in 330 ml glass containers.Various analyses were performed on the musts during fermentation as well as after fermentation.
Main results Uvaferm BC fermented to dryness with a clear preference for glucose (depletion after 118 hours versus 142 hours for fructose depletion).The two Starm. bacillaris strains fermented slower and got stuck at approximately 340 hours. Glucose remained untouched but alm…

Microbial life in grapevines: elucidating the leaf microbiome

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By Lucinda Heyns
The goal of this project was to analyse the diversity and presence of members of the bacterial microbiome found on grapevines leaves. Essentially the aim is to identify if any of these organisms have the capability to protect vines against phytopathogenic organisms. Recent studies show that plants house complex bacterial communities which is known as the ‘microbiome’ of a plant. However, very little is known about these bacteria and their roles in nature. PROJECT LAYOUT: Three cultivars, in one location were used in the study: Pinot noir, Chasselas and Solaris (a variety with higher disease resistance than the other two);Leaves were sampled three times throughout the growing season;Epiphytic and endophytic bacterial communities were quantified and their numbers present determined.
RESULTS: Epiphytes were present in higher numbers and their communities were much more diverse compared to endophytes;The upper leaf surface areas were more densely colonised than the lower le…

Effect of pruning method on phenolic profile of base sparkling wines

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By Lucinda Heyns
In this project, researchers investigated the effect of cane and spur pruning on yield and grape and wine composition of Pinot noir and Chardonnay used for the production of base sparkling wines, in a cool climate area. PROJECT LAYOUT: The study was conducted over three years (2010-2012) on a Pinot noir and Chardonnay vineyard which was planted in 1989 in Tasmania’s Coal River Valley. Vine spacing was 2.25 m x 1.5 m and the vineyard was VSP trained; From winter 2009, half of the vines were spur pruned and the other half cane pruned;Canopy assessment occurred three times during the growing season;Yield and cluster number were recorded at harvest;Wines were made according to a standard protocol.
RESULTS: 2011 was a cooler vintage than 2010 and 2012 while 2012 was much drier;In both cultivars, spur pruning showed much denser canopies that established quicker compared to the canopies of cane pruned vines;Pruning had no significant effect on total yield in either cultivar;In…